1. Field of the Invention
The present invention relates to client/server computing, and deals more particularly with techniques for providing autonomic content load balancing by dynamically selecting from among a plurality of scalable, alternative versions of content, based on run-time conditions, when preparing content for delivery to a target (such as a client workstation).
2. Description of the Related Art
The popularity of client/server computing has increased tremendously in recent years, due in large part to growing business and consumer use of the public Internet and the subset thereof known as the “World Wide Web” (or simply “Web”). Other types of client/server computing environments, such as corporate intranets and extranets, are also increasingly popular. As solutions providers focus on delivering improved Web-based computing, many of the solutions which are developed are adaptable to other client/server computing environments. Thus, references herein to the Internet and Web are for purposes of illustration and not of limitation. (Furthermore, the terms “Internet”, “Web”, and “World Wide Web” are used interchangeably herein.)
Millions of people use the Internet on a daily basis, whether for their personal enjoyment or for business purposes or both. As consumers of electronic information and business services, people now have easy access to sources on a global level. When a human user is the content requester, delays or inefficiencies in returning responses may have a very negative impact on user satisfaction, even causing the users to switch to alternative sources. Delivering requested content quickly and efficiently is therefore critical to user satisfaction. Furthermore, delivering content to end users in a timely manner may be required to meet contractual obligations.
Most modern computing applications render their displayable output using a graphical user interface, or “GUI”. In a client/server computing environment such as the Internet, client software known as a “browser” is typically responsible for requesting content from a server application and for rendering the information sent by the server in response. Commonly, the displayed information is formatted as a Web page, where the layout of the Web page is defined using a markup language such as Hypertext Markup Language (“HTML”).
Designing a Web site to serve the needs of a varied audience is a complex undertaking. A Web page providing stock quotes, for example, may be of interest to end users whose computing devices range from cellular phones and other handheld devices with limited display space to powerful desktop workstations with a relatively large amount of display space. A Web page designer may choose to focus the page layout toward the capabilities of the higher-end computing devices, in order to improve the viewing experience of that subset of the potential users. This may result in a Web page that is difficult or impossible to use from a lower-end or constrained device.
Similarly, designing a Web site that operates well under varied network conditions may be challenging. Web pages containing rich multimedia content, for example, may provide an enjoyable viewing experience for users of full-function computing devices that are connected to servers over high-speed network connections. On the other hand, if users of limited-function devices access these same pages, or if the pages are accessed using low-speed connections or during periods of network congestion, the end user may be quite displeased.
Techniques are known in the art that consider factors such as current network conditions, capabilities of the client device, and preferences of the end user when preparing content to be delivered from a server. Commonly-assigned U.S. Pat. No. 6,138,156, titled “Selecting and Applying Content-Reducing Filters Based on Dynamic Environmental Factors”, discloses techniques with which environmental factors can be used to dynamically filter the content being delivered from a server to a user's workstation. The environmental factors include characteristics of the target device, such as its available storage capacity, and billing information related to the user's account with his connection service provider. These factors are used with a rule-based approach to select a transcoding filter to be applied to a document before delivering it to a requesting user. If the end user's device has limited available storage, for example, then a color image to be rendered on a Web page might be transcoded to gray-scale, or even completely omitted, before sending content to this device.
Commonly-assigned U.S. Pat. No. 6,681,380 (Ser. No. 09/504,209, filed Feb. 15, 2000), which is titled “Aggregating Constraints and/or Preferences Using an Inference Engine and Enhanced Scripting Language”, teaches techniques for aggregating constraints and/or preferences using an inference engine and an enhanced scripting language. Values of multiple factors and the interrelationships between the factors and their values are aggregated, and the result is used to tailor or direct the processing of a software program. A rule-based system is disclosed therein for aggregating information, and based on the aggregated result, one or more transformations are performed on a requested document before transmitting it to the requester. The particular transformations to be performed may be tailored to constraints such as one or more of: the capabilities of the client device; the connection type over which the content will be delivered; the network bandwidth of the connection; the type of user agent operating on the client device; preferences of a particular user; preferences set by a systems administrator or other such person (or preferences generated in an automated manner); preferences for a particular application executing in a particular domain; etc. According to preferred embodiments of this commonly-assigned invention, the aggregated result is made available to an application program, which will use the result to tailor its own processing. This technique avoids having to change the software process itself as new values and/or new factors are deemed to be important to the aggregation result.
Commonly-assigned U.S. patent application Ser. No. 09/442,015, filed Nov. 17, 1999 (now abandoned), which is titled “Context-Sensitive Data Delivery Using Active Filtering”, discloses techniques for providing context-sensitive data delivery using active filtering to tailor the delivered data content. Preferably, a server maintains information about the typical device types to which it serves data, and continually pre-filters available data for delivery to these devices. Style sheets are used to perform one or more device-specific filtering transformations. When delivering content to a particular device, the server receives a device certificate from the device, and uses this information to identify the device type and the device's user. A user's stored preferences and/or access privileges can then be determined, and this information can be used to refine or filter information available from the server. In particular, this invention discloses filtering information to account for one or more of: an identification of a user of the device; privileges (also referred to conversely as limitations) and/or preferences of the user; the location, device type, and/or device capabilities of the user's device; and the current time.
In another prior art approach, Web sites may implement a choice of two content views, one providing high graphic content and the other providing low graphic content, thereby providing alternative views. Sometimes, the end user is given the choice of which view he wants to see (e.g., by having a graphical button on the Web page that can be clicked to select one content type or the other). Or, using a prior art “<IMG>” (image) tag in a Web page, the content designer can specify that the type of content (either an image file or a substituted text message) to be delivered to the client can be selected using factors such as device type or server load. However, this approach generally provides a binary decision, whereby a selection is limited to two choices.
What is needed are techniques that enable selecting from among a varying number of versions of content in an automated manner, thereby providing autonomic content load balancing.